Gravitational-wave astrophysics with effective-spin measurements: Asymmetries and selection biases
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PhysRevD.98.083007.pdf
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Author(s)
Zimmerman, Aaron
Chatziioannou, Katerina
Gerosa, Davide
Haster, Carl-Johan
Ng, Kwan Yeung
Vitale, Salvatore
Date Issued
October 2018
Journal
Physical Review D
Publisher
American Physical Society
Citation
Ng, Ken K. Y. et al. "Gravitational-wave astrophysics with effective-spin measurements: Asymmetries and selection biases." Physical Review D 98, 8 (October 2018): 083007 © 2018 American Physical Society
Version
Final published version
Abstract
Gravitational waves emitted by coalescing compact objects carry information about the spin of the individual bodies. However, with present detectors only the mass-weighted combination of the components of the spin along the orbital angular momentum can be measured accurately. This quantity, the effective spin χ[subscript eff], is conserved up to at least the second post-Newtonian order. The measured distribution of χ[subscript eff] values from a population of detected binaries, and in particular whether this distribution is symmetric about zero, encodes valuable information about the underlying compact-binary formation channels. In this paper we focus on two important complications of using the effective spin to study astrophysical population properties: (i) an astrophysical distribution for χ[subscript eff] values which is symmetric does not necessarily lead to a symmetric distribution for the detected effective spin values, leading to a selection bias; and (ii) the posterior distribution of χ[subscript eff] for individual events is asymmetric and it cannot usually be treated as a Gaussian. We find that the posterior distributions for χ[subscript eff] systematically show fatter tails toward larger positive values, unless the total mass is large or the mass ratio m₂/m₁ is smaller than ∼1/2. Finally we show that uncertainties in the measurement of χ[subscript eff] are systematically larger when the true value is negative than when it is positive. All these factors can bias astrophysical inference about the population when we have more than ∼100 events and should be taken into account when using gravitational-wave measurements to characterize astrophysical populations.
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
LIGO (Observatory : Massachusetts Institute of Technology)
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DOI of Published Version
https://doi.org/10.1103/PhysRevD.98.083007
